Electric heater



Aug. 14, 1928.

C. C. ABBOTT ELECTRIC HEATER Filed July 5, 1927 Inventor. Charles C. Abbott, 5 His Abborne atented Aug. 14, 192.

r l T ED CHARLES C. ABBOTT, OF PETTSFIELD, MASSACHUSETTS, ASSIGNOR T0 GENERAL ELEG- TRIO COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC HEATER.

Application filed July 5,

My invention relates to electric heaters, more particularly to electric immersion heaters, and has for its object the provision of a simple, rugged and efficient heater of this t pe.

lVfy invention has particular application to the heating of type-metal melting pots, although it obviously has various other uses'in which the heater is to be immersed. In carrying out my invention 1 provide a heater comprising a cast metal body having an electric heating unit embedded therein. This heater is arranged to be immersed in the metal to be melted in the pot and is provided with an elongated upwardly extending neck portion which terminates in a lateral extension resting on the edge of the pot whereby the heater is supported.

For a more complete understanding of my invention reference should be had to the accompanying drawing in which Fig. 1 is a side elevation view of an electric heater embodying my invention including a portion in section of a receptacle in which the heater is secured; Fig. 2 is a view mainly in section to a reduced scale showing the heater as applied to a type-metal melting pot; Fig. 3 is a sectional view of Fig. 1 taken along the line 3-3 looking in the direction of the arrows; while Fig. 4: is a fragmentary view showing the details of construction.

Referring to the drawing, 1 have shown my invention as applied to a type-metal melting pot 10, although the invention obviously has other uses. The heater constitutes a unitary cast metal body comprising an enlarged lower heating portion 11, and an upwardly extending neck portion 12 which terminates in a laterally extending supp-orting portion 13 projecting over the upper edge of the melting pot.

The lower enlarged portion 11 forms the main heating portion of the device. As shown in the drawing, it is substantially rectangular in form in a vertical plane, relatively thin in a horizontal plane, and it extends radially in the melting pot. A suitable electric heating unit is cast in this lower heating portion. This heater preferably is of the sheathed wire type, such, for example, as described and claimed in my Patent No. 1,367,- 341, dated February 1, 1921. It consists,

briefly, of a tubular metallic sheath 1 1 inwhich a helical resistor conduct-or 15 is embedded in powdered heat refractory insulat- 1927. Serial No. 203,297.

ing material 16 which is compacted to a hard dense mass so as to form a support for the resistor inside the sheath and an eflicient conductor of heat. This sheathed heating unit is bent into a plurality of vertically extending loops 17. As shown, two heating units 18 and 19 similar in shape and placed side by side are provided. The two ends of each heating unit extend upward side by side through the neck portion 12 and out at the end of the supporting portion 13, where suitable terminals are provided for connection to an electric circuit. As indicated in Fig. 3, the four lengths 20- for the two units extend upward centrally of the neck portion and are twisted together through an approximately 90 angle, as indicated by the reference numeral 21 in order that the two terminals of one unit will be directly above the two terminals of the other unit. This is for convenience in making the electrical con nections since the two units can be connected in parallel by two vertical bars.

In the construction of the heater, the two sheathed wire heating units are bent in the form indicated, placed together, and then the end portions are twisted, after which the two units are suitably supported in a mold, and metal, such as iron, is cast around them, the mold being shaped to give the desired configuration to the heater. In order to shorten the heat conducting path through the cast metal, indentations 22 are provided between the loops, as indicated in Fig. 3, whereby, it will be observed, the corresponding parallel lengths of loops are embedded in a substantially cylindrical body. Vertical heat dissipating ribs 23 and 24: are provided on.the body portion 11 at each side of the end lengths 20, since it will be observed that the rate of heat generation is highest at this point, there being four lengths of the unit together. These ribs also serve as spacers when a plurality of heaters are used, as, in fact, will ordinarily be the case. Suficient 'spacing of the heaters to assure free circulation of the molten metal between them is thus assured.

The helical resistors 15 in the units are extended up through the end lengths 20 through approximately one-half the length of the neck portion to a point somewhat above the surface of the metal in the pot in order that the neck will be heated and the metal softened around it to allow a vent for expansion of the meltingmetal in the lower portions of the pot. If the metal in the lower portion ofthe pot were melted without providing this vent, a considerable pressure, due to expansion, would be created which would eventually result in a spout of molten metal when the top metal became softened, or this pressure might, in tact, break the pot. lit will be understood that the ends of the resistors are connected to suitable terminals which extend throughout the remaining lengths of the sheaths and project therefrom.

A knife-edge bearing support 25 is pro vided on the lower side of the supporting portion 13 so as to engage the upper edge of the melting pot. The heater is further secured in place by means of a bolt 30 on each side. As shown, the portion 13 is provided at the sides with recesses 26 and 27 for the heads of the bolts and with notches 28 and 29 through which the bolts extend into tapped holes in the pot. Underneath the head of each bolt is a helical spring 30 which bears on a washer 31, resting on the bottom of the recesses 26 and 27, as the case may be, and thereby forcing the heater downward so that the knife-edge bearing 25 is held in engagement with the pot. It will be noted that the bolts 30 are placed between the knife-edge bearing and the inner side of the pot so that the springs 3O tend to hold the heater in engagement with the side of thepot, and preferably the supporting portion 13 will be at such an angle with the remainder of the heater that the heater will lie against the side wall of the pot, as indicated in the drawing. The bottom of the heater is near the bottom of the pot and has substantially the same curvature as the bottom of the pot, as indicated in Fig. 2. The projecting ends 32 of the heating units are provided with suitable terminals whereby the heaters may be connected to an electrical supply circuit.

This arrangement for securing the heater in the pot provides for a considerable movement of the heater with relation to the pot. For example, upon cooling of the metal in the pot and the shrinkage incident to cooling, it will be observed that there will be a tendency for the shrinkage to draw the heater away from the side of the pot toward the center. It the heater were clamped rigidly to the pot this would result in strains in both the heater and pot whereby one or the other might be broken. rangement disclosed, however, the springs 30 yield to permit movement of the heater without excessive strains. Furthermore, this arrangement is particularly adapted for securing the heater in various sizes of pots.

While I have described my invention as embodied in concrete form and as operating in a specific manner in accordance with the With the arprovisions of the patent statutes, it should be understood that I do not limit my invention thereto since various modifications thereof will suggestthemselves to those skilled in the art without departing from the spirit of my invention the scope of which is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. An immersion heater for type-metal pots comprising an enlarged body portion and an upwardly extending neck portion and electric heating means for said body portion extending upward into said neck portion whereby the metal is softened around said neck portion to provide a vent at the top for expansion of molten metal at the bottom of said pot.

2. An immersion heater for type-metal pots comprising a cast metal body provided with an upwardly extending neck portion, and an electric heating unit cast in said body extending upward into said neck portion whereby the metal is softened around said neck portion to provide a vent at the top for expansion of molten metal at the bottom of said pot.

3. The combination with a pot, of an electric heater in said pot having an upwardly extending neck portion, and resilient means cooperating with said neck portion so as to hold said heater against the inner side of said pot.

4. The combination with a pot, of an electric heater in said pot having an upwardly extending neck portion terminating in a laterally extending supporting portion resting on the edge of the pot, said heater being arranged to rest against the edge of the pot, a knife-edge bearing on said supporting portion, and resilient means exerting a downward force on said heater at a point between said bearing and the inner side of the pot.

5. The combination with a pot, of an eleetric heater in said pot having an upwardly extending neck portion terminating in a laterally extending supporting portion resting on the edge of the pot, a knife-edge bearing on said supporting portion, bolts secured to said pot on opposite sides of said supporting portion, and springs on said bolts applying downward t'orce to said supporting portion at points between said knife-edge bearing and the inner side of said pot.

6. An electric heater for type-metal pots comprising an enlarged cast metal body in said pot provided with an upwardly extending neck portion terminating in a laterally extending supporting portion resting on the edge of the pot, a knife-edge bearing on said supporting portion, resilient means for securing said supporting portion to the upper edge of the pot, and an electric heating unit embedded in said body.

lltl) 7. An electric heater for type-metal pots comprising a flat cast metal loody in said pot extending radially thereof, a neck portion on said body having a laterally extending supporting portion resting on the upper edge of said pot, a knife-edge bearing for said supporting portion, resilient means for holding said bearing in engagement with the edge of the pot, an insulated electrical heating resistor embedded in said body and terminals for said resistor extending through said neck portion.

In Witness whereof, I have hereunto set my hand this 30th day of June, 1927.

CHARLES C. ABJBQTT. 

